The invention concerns a storage-stable pharmaceutical preparation comprising oxycodone and naloxone.
The treatment of severe pain which results from diseases such as cancer, rheumatism and arthritis is central to the treatment of these diseases. The range of pain felt by tumor patients comprises pain of the periosteum and of the bone itself, as well as visceral pain and pain in soft tissues. All such pain forms render the daily life of patients intolerable and often lead to depressive states. Successful pain therapy resulting in a lasting improvement of quality of life for the patients is therefore equally important to the success of a comprehensive therapy, as is the treatment of the actual causes of the disease.
Regarding the importance of a successful pain therapy, the World Health Organization (WHO) has developed a 4-step model for the treatment of patients with tumor pain. This model has proven to be effective in daily routine practice and can be extended to patients suffering from chronic pain or pain forms which result from diseases other than cancer. Depending on the intensity, quality and localization of pain, four steps are distinguished during this therapy, with each next step being indicated if the effect of the pain relief agent used until then is no longer sufficient (Ebell, H. J.; Bayer A. (Ed.): Die Schmerzbehandlung von Tumorpatienten, Thieme 1994 (Supportive MaiBnahmen in der Onkologie, Band 3) and Zech, D.; Grond, S.; Lynch, J.; Hertel, D.; Lehmann, K.: Validation of World Health Organisation Guidelines for Cancer Pain Relief: a 10-year prospective study, Pain (1995), 63, 65-76).
According to this 4-step model of the WHO, opioid analgesics take a central role in treating pain. The group of opioid analgesics comprises, besides morphine which represents the prototype of these pharmaceutically active agents, also oxycodone, hydromorphone, nicomorphine, dihydrocodeine, diamorphine, papaveretum, codeine, ethylmorphine, phenylpiperidine and derivatives thereof; methadone, dextropropoxyphene, buprenorphine, pentazocine, tilidine, tramadol and hydrocodone. The ATC-Classification (Anatomical Therapeutic Chemical Classification) of the WHO indicates whether the pharmaceutically active agent represents an opiod analgesic, or not. The pronounced pain-relieving effect of opioid analgesics is due to the imitation of the effect of endogenous, morphine-like acting substances (“endogenous opioids”), whose physiological function is to control the reception and processing of pain stimuli.
Opioids repress the propagation of pain stimuli. Besides the immediate inhibition of neuronal excitatory signal transduction in the spinal cord caused by opioids, an activation of such nerve tracts is relevant, which project form the brainstem into the spinal cord. This activation results in an inhibition of pain propagation in the spinal cord. Moreover, opioids limit the pain reception of the thalamus and by affecting the limbic system they influence the affective pain evaluation.
Opioid receptors are found at different sites in the body. Receptors of the intestine and brain are of particular importance for pain therapy by opioids, especially as their occupation results in different side effects.
Opioid analgesics are considered to be strong agonists if they bind with high affinity to opioid receptors and induce a strong inhibition of pain reception. Substances that also bind with high affinity to opioid receptors, but that do not provoke a reduction of pain reception and which thereby counteract the opioid agonists, are designated as antagonists. Depending on the binding behaviour and the induced activity, opioids can be classified as pure agonists, mixed agonists/antagonists and pure antagonists. Pure antagonists comprise, for example, naltrexone, naloxone, nalmefene, nalorphine, nalbuphine, naloxoneazinen, methylnaltrexone, ketylcyclazocine, norbinaltorphimine, naltrindol, 6-ß-naloxol und 6-ß-naltrexol (Forth W.; Henschler, D.; Rummel W.; Starke, K.: Allgemeine und Spezielle Pharmakologie und Toxikologie, 7. Auflage, 1996, Spektrum Akademischer Verlag, Heidelberg Berlin Oxford).
Due to their good analgesic efficiency compounds such as oxycodone, tilidine, buprenorphine und pentazocine, have been used in the form of medicaments for pain therapy. Medicaments such as Oxigesic® (wherein oxycodone is the analgesic active compound) und Valoron® (wherein tilidine is the analgesic active compound) have proven valuable for pain therapy.
However, use of opioid analgesics for pain therapy might go along with undesirable side effects. Thus, long-term use of opioid analgesics can lead to psychological and physical dependence.
Especially the physical dependence of patients suffering from pain to opioid analgesics leads to the development of tolerance, meaning that upon extended intake, increasingly higher doses of the pain relieving agent have to be taken by the patient, in order to experience pain relief. The euphoregenic effect of opioid analgesics often leads to the abuse of pain relievers. Drug abuse and psychological dependence are a common phenomenon, especially among teenagers. These dangerous effects are especially caused by the substances with strong analgesic capacity, and can range from undesired habituation to fully developed addiction. However, these substances are legitimately used for medical purposes and medicine cannot do without them.
Besides the mentioned disadvantages, the use of potent opioid analgesics for pain therapy often also lead to undesirable side effects, such as obstipation, breath depression, sickness and sedation. Less frequently, the urge or the disability to pass water are observed. Different attempts have been made to counteract the habituation processes and the other side effects occurring during pain therapy. This can be done, e.g. by traditional treatment methods. In the case of drug addiction this might be a drug withdrawal treatment, and in the case of obstipation, this might be done by administration of laxatives.
Other attempts aim at minimizing the addictive and habituation forming potential of opioid analgesics, as well as their other side effects by the administration of antagonists which counteract the opioid analgesic. Such antagonists might be naltrexone or naloxone.
There have been numerous proposals and suggestions, how the application of the aforementioned active compounds could be used to avoid undesired habituation and dependence, or even addiction.
U.S. Pat. Nos. 3,773,955 and 3,966,940 suggested to formulate analgesics in combination with naloxone, in order to prevent dependence-promoting effects such as euphoria and the like, upon parenteral application. The avoidance of side effects such as obstipation has not been addressed.
To limit the parenteral abuse of oral application forms, U.S. Pat. No. 4,457,933 suggested the combination of morphine with naloxone in defined ranges. The avoidance of side effects such as obstipation has also not been mentioned.
U.S. Pat. No. 4,582,835 describes, again in order to avoid abuse, a preparation comprising a combination of buprenorphine and naloxone that is to be administered either parenterally or sublingually.
European application EP 0 352 361 A1 concerns the treatment of obstipation during pain therapy by the oral application of an opioid analgesic and one antagonist, with the antagonist being a pro-drug form of either naltrexone or naloxone. Avoidance of abuse of the opioid analgesic is not an issue in this application.
German patent application DE 43 25 465 A1 also concerns the treatment of obstipation during pain therapy using a preparation which comprises an opioid analgesic and an antagonist. The characterizing feature of this disclosure is that the antagonist which can be naloxone, has to be present in higher amounts than the opioid analgesic which is preferably morphine. This is to ensure that the antagonist unfolds its anti-obstipation effect without reducing the analgesic activity of the agonist. The avoidance of abuse of the opioid analgesic is not an issue in this application.
In order to avoid side effects such as obstipation and breath depression during pain therapy, preparations have been introduced on the market which can be taken orally and comprise an opioid analgesic and the opioid antagonist, naloxone. The medicament Talwin® of Windrop/Sterling comprises pentazocine and naloxone. The medicament Valoron® of Gödeke comprises a tilidine-naloxone combination.
Besides the potent analgesic effect, the reduction of addictive potential and the avoidance of side effects, medicaments usable for a successful pain therapy should provide for additional characteristics.
Generally, medicaments have to be formulated in a way that the active compounds are stable as long as possible, under standard storage conditions. Medicaments have also to be formulated in a way that the intended release profiles of the active compounds do not change upon long-term storage.
Additionally, (also in the case of agonist/antagonist-combinations) the release profile of each single active compound should be selectable as required. The measures applied in order to achieve this should not hamper or even prevent that the release profiles of additional active compounds (e.g. in the case of combinations of different active compounds) can be chosen as required. Consequently, there should be no mutual dependency of the release profiles.
Medicaments suitable for pain therapy should either contain the active compounds in such amounts or be formulated in such ways that they have to be taken by the patients only rarely. The easier the application scheme for a pain reliever is, and the more evident it is for the patient why and how often he should take which tablet, the more exactly he will adhere to the physician's orders. The necessity to take the pain reliever only infrequently, will result in a high willingness of the patient to take the pain reliever (compliance).
Through the use of so called sustained-release formulations, i.e. formulations of medicaments from which the active compounds are released over an extended period of time, it has been tried to lower the frequency by which pain relieving medicaments have to be taken, and thereby to increase the compliance of patients. Such sustained-release formulations also make sense in that the sustained release of an opioid analgesic reduces the addictive potential of this active compound.
This is due to the fact that the addictive potential of an active compound is not defined by the compound itself, but rather by the way it is administered and the pharmaco-dynamics resulting therefrom. Besides the psychotropic effect of an opioid, the rate by which the brain encounters an opioid, is more decisive criterion for the risk of dependency than the active compound itself (Nolte, T.; STKZeitschrift für angewandte Schmerztherapie, 2001, Vol. 2).
The medicament Oxigesic® of Purdue is a preparation from which the opioid analgesic oxycodone is released in a sustained manner. cDue to this formulation, the frequency by which the medicament has to be taken as well as the addictive potential is lowered, however the side effects remain and the danger of developing addiction cannot be excluded, as Oxigesic® does not contain opioid-antagonists.
According to the already mentioned European patent application EP 0 352 361 A, neither the opioid analgesic nor the antagonist are formulated to be released in a sustained manner. Accordingly, the time period during which such preparations are effective is limited and preparations have to be taken multiple times per day. The desired compliance of the patient is not achieved. This application also does not disclose the advantages of formulations of preparations that are characterized by a time-stable and independent release of the active compounds. The storage stability of such preparations is also not addressed by this disclosure.
German patent application DE 43 25 465 A1 discloses formulations according to which obstipation occurring during pain therapy is prevented by the sustained release of the opioid agonist while the antagonist, which is present in excess must not be released in a sustained manner. Due to the high First-Pass-Effect of naloxone, comparably large amounts of this compound have therefore to be used. This application discloses neither the advantages nor the formulations of preparations, which are characterized by time-stable and independent release of the active compounds. The storage stability of such preparations is also not an issue of this disclosure. A doctor using preparations according to this disclosure has therefore to carry out extensive titration experiments each time he wants to increase the dosage.
The company Gödeke offers, under the trademark Valoron®, a pain reliever that comprises a tilidine-naloxone-combination. According to the product literature, a formulation is used from which both active compounds are released in a sustained manner. The matrix used comprises a relevant part of water-swellable material (HPMC) and has therefore to be considered as a swellable (and possibly partially erosive) diffusion matrix. A disadvantage of this known formulation is that tilidine and naloxone, given identical mass ratios but different absolute amounts, show different release profiles. The release rates of the agonist and the antagonist are not independent from each other, which is probably due to the sustained release formulation used. Accordingly, it is necessary for the physician to carry out extensive titration experiments for each individual patient if he wants to increase the dosage even though he does not change the mass ratio of tilidine:naloxone, as he cannot assume that the release profiles of both components will remain constant. The range of therapeutically usable amounts of the analgesic that are available to the doctor is therefore limited.